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Add a check to replace concatenated multiline strings with text blocks
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core/src/main/java/com/google/errorprone/bugpatterns/StringConcatToTextBlock.java
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| /* | ||
| * Copyright 2024 The Error Prone Authors. | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
|
|
||
| package com.google.errorprone.bugpatterns; | ||
|
|
||
| import static com.google.common.collect.ImmutableList.toImmutableList; | ||
| import static com.google.common.collect.Iterables.getLast; | ||
| import static com.google.common.collect.Iterables.getOnlyElement; | ||
| import static com.google.errorprone.BugPattern.SeverityLevel.WARNING; | ||
| import static com.google.errorprone.matchers.Description.NO_MATCH; | ||
| import static com.google.errorprone.matchers.method.MethodMatchers.constructor; | ||
| import static com.google.errorprone.matchers.method.MethodMatchers.instanceMethod; | ||
| import static com.google.errorprone.matchers.method.MethodMatchers.staticMethod; | ||
| import static com.google.errorprone.util.ASTHelpers.getReceiver; | ||
| import static com.google.errorprone.util.ASTHelpers.getStartPosition; | ||
| import static com.google.errorprone.util.ASTHelpers.getType; | ||
| import static com.google.errorprone.util.ASTHelpers.isSameType; | ||
| import static java.util.stream.Collectors.joining; | ||
|
|
||
| import com.google.common.collect.ImmutableList; | ||
| import com.google.common.collect.Streams; | ||
| import com.google.errorprone.BugPattern; | ||
| import com.google.errorprone.VisitorState; | ||
| import com.google.errorprone.bugpatterns.BugChecker.LiteralTreeMatcher; | ||
| import com.google.errorprone.bugpatterns.BugChecker.MethodInvocationTreeMatcher; | ||
| import com.google.errorprone.fixes.SuggestedFix; | ||
| import com.google.errorprone.matchers.Description; | ||
| import com.google.errorprone.matchers.Matcher; | ||
| import com.google.errorprone.util.ASTHelpers; | ||
| import com.google.errorprone.util.ErrorProneToken; | ||
| import com.google.errorprone.util.ErrorProneTokens; | ||
| import com.google.errorprone.util.SourceCodeEscapers; | ||
| import com.sun.source.tree.BinaryTree; | ||
| import com.sun.source.tree.ExpressionTree; | ||
| import com.sun.source.tree.LineMap; | ||
| import com.sun.source.tree.LiteralTree; | ||
| import com.sun.source.tree.MethodInvocationTree; | ||
| import com.sun.source.tree.NewClassTree; | ||
| import com.sun.source.tree.Tree; | ||
| import com.sun.tools.javac.parser.Tokens; | ||
| import java.util.ArrayDeque; | ||
| import java.util.Deque; | ||
| import java.util.List; | ||
| import java.util.Optional; | ||
| import java.util.stream.Stream; | ||
|
|
||
| /** A {@link BugChecker}; see the associated {@link BugPattern} annotation for details. */ | ||
| @BugPattern( | ||
| summary = "This string literal can be written more clearly as a text block", | ||
| severity = WARNING) | ||
| public class StringConcatToTextBlock extends BugChecker | ||
| implements LiteralTreeMatcher, MethodInvocationTreeMatcher { | ||
|
|
||
| public static final String DELIMITER = "\"\"\""; | ||
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|
||
| @Override | ||
| public Description matchLiteral(LiteralTree tree, VisitorState state) { | ||
| // javac constant folds string concat during parsing, so we don't need to handle binary | ||
| // expressions | ||
| // see -XDallowStringFolding=false | ||
| if (!tree.getKind().equals(Tree.Kind.STRING_LITERAL)) { | ||
| return NO_MATCH; | ||
| } | ||
| if (state.getPath().getParentPath().getLeaf() instanceof BinaryTree parent) { | ||
| if (parent.getKind().equals(Tree.Kind.PLUS) | ||
| && isSameType(getType(parent), state.getSymtab().stringType, state)) { | ||
| // the readability benefit of text blocks is less if they're inside another string | ||
| // concat expression | ||
| return NO_MATCH; | ||
| } | ||
| } | ||
| List<ErrorProneToken> tokens = state.getTokensForNode(tree); | ||
| ImmutableList<String> strings = | ||
| tokens.stream() | ||
| .filter(t -> t.kind().equals(Tokens.TokenKind.STRINGLITERAL)) | ||
| .map(t -> t.stringVal()) | ||
| .collect(toImmutableList()); | ||
| boolean trailingNewline = getLast(strings).endsWith("\n"); | ||
| // Only migrate if there are enough lines to make it worthwhile. Escaping the trailing newline | ||
| // slightly reduces the readability benefit of migrating, so require an extra line to make it | ||
| // worth it. | ||
| int thresholdToMigrate = trailingNewline ? 2 : 3; | ||
| if (strings.size() < thresholdToMigrate) { | ||
| return NO_MATCH; | ||
| } | ||
| // only migrate if each piece of the string concat ends in an escaped newline. It would be | ||
| // possible to migrate more eagerly, and perhaps use escaped newlines to reflow the string, or | ||
| // recognize APIs that don't care about extra newlines. | ||
| if (!strings.stream().limit(strings.size() - 1).allMatch(s -> s.endsWith("\n"))) { | ||
| return NO_MATCH; | ||
| } | ||
| // shared logic in 'match' assumes the strings are split at newline boundaries, so trim the | ||
| // escaped newlines here | ||
| strings = | ||
| Streams.concat( | ||
| strings.stream().limit(strings.size() - 1).map(s -> s.substring(0, s.length() - 1)), | ||
| Stream.of(getLast(strings))) | ||
| .collect(toImmutableList()); | ||
| return match(tree, strings, state); | ||
| } | ||
|
|
||
| @Override | ||
| public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) { | ||
| if (JOINER_JOIN.matches(tree, state)) { | ||
| return joiner(tree, state); | ||
| } | ||
| if (STRING_JOINER_TO_STRING.matches(tree, state)) { | ||
| return stringJoiner(tree, state); | ||
| } | ||
| if (STRING_JOIN.matches(tree, state)) { | ||
| return stringJoin(tree, state); | ||
| } | ||
| if (FOR_SOURCE_LINES.matches(tree, state)) { | ||
| return forSourceLines(tree, state); | ||
| } | ||
| return NO_MATCH; | ||
| } | ||
|
|
||
| private Description match(Tree replace, ImmutableList<String> lines, VisitorState state) { | ||
| return match(replace, getStartPosition(replace), state.getEndPosition(replace), lines, state); | ||
| } | ||
|
|
||
| private Description match( | ||
| Tree tree, | ||
| int replaceFrom, | ||
| int replaceTo, | ||
| ImmutableList<String> strings, | ||
| VisitorState state) { | ||
| if (strings.isEmpty()) { | ||
| return NO_MATCH; | ||
| } | ||
| ImmutableList<ErrorProneToken> tokens = | ||
| ErrorProneTokens.getTokens( | ||
| state.getSourceCode().subSequence(replaceFrom, replaceTo).toString(), state.context); | ||
| if (!tokens.stream() | ||
| .flatMap(t -> t.comments().stream()) | ||
| .map(c -> c.getText()) | ||
| .allMatch(x -> x.isEmpty())) { | ||
| // For long string literals with interspersed comments, moving all the comments to the | ||
| // beginning could regress readability. | ||
| // TODO: cushon - handle comments? | ||
| return NO_MATCH; | ||
| } | ||
| // bail out if the contents contain a delimiter that would require escaping | ||
| if (strings.stream().anyMatch(s -> s.contains(DELIMITER))) { | ||
| return NO_MATCH; | ||
| } | ||
| boolean trailingNewline = getLast(strings).endsWith("\n"); | ||
| strings = | ||
| String.join("\n", strings) | ||
| .stripIndent() | ||
| .lines() | ||
| .map(s -> s.stripTrailing()) | ||
| .collect(toImmutableList()); | ||
| LineMap lineMap = state.getPath().getCompilationUnit().getLineMap(); | ||
| String indent = " ".repeat((int) lineMap.getColumnNumber(replaceFrom) - 1); | ||
| String suffix = trailingNewline ? "" : "\\"; | ||
| String replacement = | ||
| strings.stream() | ||
| .map(line -> line.isEmpty() ? line : (indent + line)) | ||
| .map(SourceCodeEscapers.getJavaTextBlockEscaper()::escape) | ||
| .collect(joining("\n", DELIMITER + "\n", suffix + "\n" + indent + DELIMITER)); | ||
| SuggestedFix fix = SuggestedFix.replace(replaceFrom, replaceTo, replacement); | ||
| return describeMatch(tree, fix); | ||
| } | ||
|
|
||
| private static final Matcher<ExpressionTree> JOINER_JOIN = | ||
| instanceMethod().onExactClass("com.google.common.base.Joiner").named("join"); | ||
| private static final Matcher<ExpressionTree> JOINER_ON = | ||
| staticMethod().onClass("com.google.common.base.Joiner").named("on"); | ||
|
|
||
| private static final Matcher<ExpressionTree> STRING_JOINER_TO_STRING = | ||
| instanceMethod().onExactClass("java.util.StringJoiner").named("toString"); | ||
| private static final Matcher<ExpressionTree> STRING_JOINER_ADD = | ||
| instanceMethod().onExactClass("java.util.StringJoiner").named("add"); | ||
| private static final Matcher<ExpressionTree> STRING_JOINER_CONSTRUCTOR = | ||
| constructor().forClass("java.util.StringJoiner").withParameters("java.lang.CharSequence"); | ||
|
|
||
| private static final Matcher<ExpressionTree> STRING_JOIN = | ||
| staticMethod().onClass("java.lang.String").named("join"); | ||
|
|
||
| private static final Matcher<ExpressionTree> FOR_SOURCE_LINES = | ||
| staticMethod().onClass("com.google.testing.compile.JavaFileObjects").named("forSourceLines"); | ||
|
|
||
| private Description joiner(MethodInvocationTree tree, VisitorState state) { | ||
| ImmutableList<String> strings = stringLiteralArguments(tree.getArguments()); | ||
| if (strings.isEmpty()) { | ||
| return NO_MATCH; | ||
| } | ||
| if (!(getReceiver(tree) instanceof MethodInvocationTree receiver)) { | ||
| return NO_MATCH; | ||
| } | ||
| if (!JOINER_ON.matches(receiver, state)) { | ||
| return NO_MATCH; | ||
| } | ||
| if (!newlineLiteral(getOnlyElement(receiver.getArguments()))) { | ||
| return NO_MATCH; | ||
| } | ||
| return match(tree, strings, state); | ||
| } | ||
|
|
||
| private Description stringJoiner(MethodInvocationTree tree, VisitorState state) { | ||
| Deque<String> strings = new ArrayDeque<>(); | ||
| ExpressionTree current = tree; | ||
| while (getReceiver(current) instanceof MethodInvocationTree receiver) { | ||
| if (!STRING_JOINER_ADD.matches(receiver, state)) { | ||
| break; | ||
| } | ||
| Optional<String> string = stringLiteral(getOnlyElement(receiver.getArguments())); | ||
| if (string.isEmpty()) { | ||
| return NO_MATCH; | ||
| } | ||
| strings.addFirst(string.get()); | ||
| current = receiver; | ||
| } | ||
| if (!(getReceiver(current) instanceof NewClassTree constructor | ||
| && STRING_JOINER_CONSTRUCTOR.matches(constructor, state))) { | ||
| return NO_MATCH; | ||
| } | ||
| if (!newlineLiteral(getOnlyElement(constructor.getArguments()))) { | ||
| return NO_MATCH; | ||
| } | ||
| return match(tree, ImmutableList.copyOf(strings), state); | ||
| } | ||
|
|
||
| private Description stringJoin(MethodInvocationTree tree, VisitorState state) { | ||
| ImmutableList<String> strings = | ||
| stringLiteralArguments(tree.getArguments().subList(1, tree.getArguments().size())); | ||
| if (!newlineLiteral(tree.getArguments().get(0))) { | ||
| return NO_MATCH; | ||
| } | ||
| return match(tree, strings, state); | ||
| } | ||
|
|
||
| private Description forSourceLines(MethodInvocationTree tree, VisitorState state) { | ||
| ImmutableList<String> strings = | ||
| stringLiteralArguments(tree.getArguments().subList(1, tree.getArguments().size())); | ||
| return match( | ||
| tree.getArguments().get(1), | ||
| getStartPosition(tree.getArguments().get(1)), | ||
| state.getEndPosition(getLast(tree.getArguments())), | ||
| strings, | ||
| state); | ||
| } | ||
|
|
||
| private static boolean newlineLiteral(ExpressionTree expressionTree) { | ||
| Object value = ASTHelpers.constValue(expressionTree); | ||
| if (value == null) { | ||
| return false; | ||
| } | ||
| return value.equals("\n") || value.equals('\n'); | ||
| } | ||
|
|
||
| static ImmutableList<String> stringLiteralArguments(List<? extends ExpressionTree> arguments) { | ||
| ImmutableList<String> strings = | ||
| arguments.stream() | ||
| .filter(a -> a.getKind().equals(Tree.Kind.STRING_LITERAL)) | ||
| .map(x -> (String) ((LiteralTree) x).getValue()) | ||
| .collect(toImmutableList()); | ||
| if (strings.size() != arguments.size()) { | ||
| return ImmutableList.of(); | ||
| } | ||
| return strings; | ||
| } | ||
|
|
||
| static Optional<String> stringLiteral(ExpressionTree tree) { | ||
| return tree.getKind().equals(Tree.Kind.STRING_LITERAL) | ||
| ? Optional.of((String) ((LiteralTree) tree).getValue()) | ||
| : Optional.empty(); | ||
| } | ||
| } |
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